The behavioural, endocrine and immune responses of sheep to isolation

Two groups of 5 sheep (7 months of age) were moved and isolated in pens which did not allow visual and tactile contact with other sheep for 24 h. They were then moved back to their original pens where visual and tactile contact was possible. After 24 h the procedure was repeated 7 times for one group and 13 times for the other group. One group (control) of 5 sheep remained in pens where visual and tactile contact was possible. When isolated the lambs spent more time standing still in an alert posture, less time eating and resting, and vocalized more than control lambs. The heart rate of the lambs increased when they were moved between pens and during isolation. The plasma concentration of cortisol was significantly increased after 1.5 h and 3 h of isolation. The plasma concentration of prolactin was increased after 1.5 h of isolation. After 3 h of isolation the number of neutrophils in the blood was increased and the numbers of T lymphocytes (CD2), T-helper lymphocytes (CD4) and γδ lymphocytes (T19) were decreased. After 24 h of isolation the lymphocyte blastogenic response to Con A was lower and the number of T lymphocytes and T-helper lymphocytes were still less than those in control lambs. Although there were still behavioural changes when the lambs were isolated for the 7th time, no changes in cortisol, prolactin or leukocytes were observed. It is concluded that stressors similar to isolation, which can occur during normal management practice, may elicit short-term leukocyte changes in lambs.